Coating composition for green sheet, green sheet, method for producing green sheet, and method for producing electronic component

ABSTRACT

A green sheet coating material including ceramic powder, a binder resin including a butyral based resin as the main component, and a solvent. The solvent includes a first solvent medium having a relatively low boiling point, wherein said binder resin is easy to be dissolved, and a second solvent medium having a relatively high boiling point. The boiling point of the second solvent medium is in a range of 130 to 230° C. The second solvent medium is included by 5 to 70 wt %, and more preferably 8 to 52 wt % with respect to 100 wt % of the entire solvent.

TECHNICAL FIELD

The present invention relates to a green sheet coating material, a greensheet, a production method of a green sheet and a production method ofan electronic device, and particularly relates to a coating material,green sheet and a method capable of producing a green sheet without apin hole, having excellent surface smoothness even in the case of anextremely thin sheet and being suitable to making an electronic deviceof a thin layer and multilayer.

BACKGROUND ART

In recent years, as a variety of electronic equipments become compact,electronic devices to be installed inside the electronic equipments havebecome more compact and higher in performance. As one of the electronicdevices, there is a ceramic electronic device, such as a CR built-insubstrate and a multilayer ceramic capacitor, and the ceramic electronicdevices have been required to be more compact and higher in performance.

To pursue a more compact ceramic electronic device having a highercapacity, there is a strong demand for making a dielectric layerthinner. Recently, a thickness of a dielectric green sheet composing adielectric layer has become several μm or less.

To produce a ceramic green sheet, normally, a ceramic coating materialcomposed of ceramic powder, a binder (an acrylic based resin and abutyral based resin, etc.), a plasticizer (phthalate esters, glycols,adipic acids, and phosphoric esters) and an organic solvent (toluene,MEK and acetone, etc.). Next, the ceramic coating material coated on acarrier sheet (a supporting body made by PET and PP) by using the doctorblade method, etc. and dried by heating.

Also, a method of producing by preparing a ceramic suspension whereinthe ceramic powder and binder are mixed in a solvent, then, extruding afilm-shaped molded item obtained by molding the suspension by twin-screwhas been considered in recent years.

A method of producing a multilayer ceramic capacitor by using theceramic green sheet explained above will be explained in detail. Aninternal electrode conductive paste containing metal powder and a binderis printed to be a predetermined pattern on the ceramic green sheet anddried to form an internal electrode pattern. After that, the green sheetis peeled from the carrier sheet and stacked by a predetermined numberof layers. Here, two methods are proposed, that are a method of peelingthe green sheet from the carrier sheet before stacking in layers and amethod of peeling the carrier sheet after stacking in layers andadhering by compression, but the difference is not large. Finally, thestacked body is cut to be chips, so that green chips are prepared. Afterfiring the green chips, external electrodes are formed, so that amultilayer ceramic capacitor and other electronic devices are produced.

When producing a multilayer ceramic capacitor, an interlayer thicknessof sheets formed with internal electrodes is in a range of 3 μm to 100μm or so based on a desired capacitance required as a capacitor. Also,in a multilayer ceramic capacitor, a part not formed with internalelectrodes is formed on an outer part in the stacking direction of thecapacitor chip.

Generally, when a thickness of the green sheet becomes thin, there ariseproblems that smoothness on the surface of the sheet declines andstacking becomes difficult.

In recent years, as electronic equipments become more compact,electronic devices to be used therein have rapidly become more compact.In multilayer electronic devices as typified by a multilayer ceramiccapacitor, rapid development has been made on increasing the number oflayers to be stacked and attaining a thinner interlayer thickness. Torespond to the technical trends, a thickness of a green sheet, whichdetermines the interlayer thickness, has almost become 3 μm or less to 2μm or less. Therefore, in a production process of a multilayer ceramiccapacitor, it is necessary to handle extremely thin green sheets and todesign very advanced green sheet properties.

As characteristics required as the properties of such an extremely thingreen sheet, sheet strength, flexibility, smoothness, adhesiveness whenbeing stacked, handlability (electrostatic property), etc. may bementioned, and balance of a higher order is required.

Particularly, when the sheet becomes thin, roughness (unevenness) on thesheet surface cannot be ignored with respect to the thickness. Namely,there appears a portion where the sheet is thin. It is anticipated thatthis portion has susceptibility to a voltage application at firing andcauses short-circuiting. Therefore, to produce a sheet having a unifiedthickness and smooth surface is essential element technique in producinga multilayer chip capacitor.

Note that, as described in the Japanese Unexamined Patent PublicationNo. 6-206756, there is known a technique of using a polyvinyl butyralresin having a polymerization degree of 1000 or more as a binder ingreen sheet slurry containing an aqueous solvent for a purpose ofeliminating a short-circuiting defect.

However, the Japanese Unexamined Patent Publication No. 6-206756 is notfor particularly attaining a thinner organic solvent based green sheet,and also has the problem that surface smoothness declines and stackingbecomes difficult when a thickness of the green sheet is made thin.

Also, the Patent Publication No. 2866137 discloses a technique of usinga solvent having a high evaporation rate to improve a surface propertyof the sheet by making the evaporation rate high. However, although themethod of making the evaporation rate high is effective to obtain athick sheet, it gives an adverse effect of deteriorating the surfaceproperty in the case of making the sheet thin.

Also, as disclosed in the Japanese Unexamined Patent Publication No.2000-335971, there is known an invention of regulating a blendingcomposition ratio, a defoaming condition and a drying temperaturecondition of the sheet by an aqueous coating material.

However, in this technique, a sheet having a desired property may not beable to be obtained due to the limited composition and the procedurebecomes cumbersome and complicated because a defoaming step is added.

Furthermore, as disclosed in the Japanese Unexamined Patent PublicationNo. 2001-114568, there is also known a technique of improving a surfaceproperty by extending the sheet by applying pressure.

However, in this technique, the sheet may be damaged due to the appliedpressure when the green sheet is made thin.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a coating material, agreen sheet and a method capable of producing a green sheet without apin hole, having enough strength to be peeled from a supporting body andexcellent surface smoothness even when the green sheet is extremelythin, and being suitable to make an electronic device thin andmultilayer.

The present inventors have been committed themselves to study to attainthe above objects, found that it was possible to produce a green sheetwithout a pin hole and having enough strength to be peeled from asupporting body and excellent surface smoothness even if the green sheetwas extremely thin, by using as a binder a polyvinyl acetal resin orother butyral based resin and by making a second solvent medium having arelatively high boiling point contained as a solvent in addition to afirst solvent medium having a relatively low boiling point, wherein abinder resin was easy to be dissolved, and completed the presentinvention.

Namely, green sheet coating material according to the present inventioncontains ceramic powder, a binder resin including a butyral based resinas the main component, and a solvent, wherein

the solvent contains a first solvent medium having a relatively lowboiling point, wherein the binder resin is easy to be dissolved, and asecond solvent medium having a relatively high boiling point.

By using a binder resin including a butyral based resin as the maincomponent and by making a second solvent medium having a relatively highboiling point contained as a solvent in addition to a first solventmedium having a relatively low boiling point, wherein a binder resin iseasy to be dissolved, it becomes possible to produce a green sheetwithout a pin hole and having enough strength to be peeled from asupporting body and excellent surface smoothness even if the green sheetis extremely thin. For example, a thickness of a dielectric layer afterfiring (a green sheet after firing) can be made as thin as 5 μm or less,preferably 3 μm or less, and furthermore preferably 2 μm or less. Also,the number of layers to be stacked can be increased. Furthermore,short-circuiting or other defects can be reduced.

Preferably, a vapor pressure of the second solvent medium at the roomtemperature (25° C.) is lower than that of the first solvent medium. Itis liable that a vapor pressure generally becomes low in the solventhaving a high boiling point.

Preferably, a boiling point of the second solvent medium is in a rangeof 130 to 230° C., and more preferably 135 to 210° C. When the boilingpoint is too low, it is liable that an evaporation rate of the solventbecomes high when drying the green sheet, and the sheet surface becomesrough. While, when the boiling point is too high, drying of the sheettakes time and there is a tendency that it becomes difficult to make asheet.

Preferably, a vapor pressure of the second solvent medium at 25° C. isin a range of 1.3 to 667 Pa (0.01 to 5 Torr), and more preferably in arange of 10 to 300 Pa. When the vapor pressure is too low, drying of thesheet takes time and there is a tendency that it becomes difficult tomake a sheet. While, when the vapor pressure is too high, an evaporationrate of the solvent becomes high when drying the green sheet and thesheet surface becomes rough.

Preferably, when assuming that a boiling point of the second solventmedium is T° C. and a vapor pressure of the second solvent medium at 25°C. is α Pa, a product of T×α is in a range of 2000 to 65000 (° C.×Pa),and more preferably in a range of 3000 to 50000. Since the rising rateof the boiling point is larger than the lowering rate of the vaporpressure, a product of T×α in the ranges is preferable. Note that thereare some solvent, wherein the boiling point is high but the vaporpressure is also high. In the present invention, it is preferable that asolvent having a high boiling point and a low vapor pressure is includedas a second solvent medium.

Preferably, the second solvent medium has a higher boiling point by 50to 105° C. than a drying temperature at the time of making the greensheet coating material to be a sheet. By making the second solventmedium having such a high boiling point contained in the coatingmaterial, the effects of the present invention are enhanced.

Preferably, a drying temperature at the time of drying the green sheetis 50 to 100° C.

Preferably, the second solvent medium includes an organic solvent havinga higher boiling point by 60 to 150° C. than that of alcohol having thelowest boiling point included in the first solvent medium. By making thesecond solvent medium having such a high boiling point contained in thecoating material, the effects of the present invention are enhanced.

Preferably, the second solvent medium includes an organic solvent havinga vapor pressure at 25° C. of 0.1 to 10% of that of alcohol having thehighest vapor pressure at 25° C. included in the first solvent medium.By making the second solvent medium having such a low vapor pressurecontained in the coating material, the effects of the present inventionare enhanced.

Preferably, the second solvent medium is included by 5 to 70 wt %, morepreferably 8 to 52%, and furthermore preferably 13 to 52 wt % withrespect to 100 wt % of the entire solvent. When the content of thesecond solvent medium is too small, effects of the present invention aresmall, while when too much, it tends to be difficult to make a sheet.

Preferably, the second solvent medium is not particularly limited as faras it has a high boiling point and a butyral based resin is dissolvedtherein, but it includes at least one selected form the 1) to 3) below.

1) monohydric alcohol having a carbon number of 5 to 9

1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, tarpineol

2) ketones containing a cyclic structure

cyclohexanon, isophorone

3) compound containing two or more functional groups selected from a —OHgroup, ether and ketone

2-ethoxyethanol, 2-butoxyethanol, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diacetone alcohol

The first solvent medium is not particularly limited as far as it has alow boiling point and a butyral based resin is dissolved therein.Preferably, at least one of ethanol and methanol is contained.

Preferably, the butyral based resin is a polybutyral resin; and

a polymerization degree of the polybutyral resin is 1000 or more and1700 or less, a butyralation degree of the resin is 64% or higher and78% or lower, and a residual acetyl group amount is less than 6%.

When the polymerization degree of the polybutyral resin is too low, itis liable that sufficient mechanical strength is hard to be obtainedwhen the layer is made to be as thin as 5 μm or less, and preferably 3μm or less. While, when the polymerization degree is too high, surfaceroughness tends to deteriorate when made to be a sheet. Also, when thebutyralation degree of the polybutyral resin is too low, solubility to acoating material tends to deteriorate, while when too high, surfaceroughness of the sheet tends to deteriorate. Furthermore, when aresidual acetyl group amount is too much, surface roughness of the sheettends to deteriorate.

Preferably, the binder resin is included by 5 parts by weight or moreand 6.5 parts by weight or less with respect to 100 parts by weight ofthe ceramic powder. When a content of the binder resin is too small, itis liable that the sheet strength declines and stackability(adhesiveness at the time of stacking) deteriorates. Also, when acontent of the binder resin is too large, it is liable that segregationof the binder resin is caused to deteriorate the dispersibility, andsheet surface roughness declines.

Preferably, dioctyl phthalate as a plasticizer is contained by 40 partsby weight or more and 70 parts by weight or less with respect to 100parts by weight of the binder resin. Comparing with other plasticizers,dioctyl phthalate is preferable in terms of both of sheet strength andsheet ductility, and particularly preferable because the releasestrength from a supporting body is small and it is easily peeled. Notethat when a content of the plasticizer is too small, it is liable thatsheet stretching becomes less and flexibility becomes less. Also, whenthe content is too large, it is liable that breedout of the plasticizerfrom the sheet is caused, segregation of the plasticizer is easilycaused against the sheet, and the sheet dispersibility declines.

A production method of a ceramic green sheet according to the presentinvention comprises the steps of:

preparing the green sheet coating material; and

forming a ceramic green sheet by using the green sheet coating material.

A production method of a ceramic electronic device according to thepresent invention comprises the steps of:

preparing the green sheet coating material;

forming a ceramic green sheet by using the green sheet coating material;

drying the green sheet;

stacking the green sheets after drying via an internal electrode layerto obtain a green chip; and

firing the green chip.

The green sheet according to the present invention is produced by usingthe green sheet coating material explained above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a multilayer ceramic capacitoraccording to an embodiment of the present invention;

FIG. 2 is a sectional view of a key part showing a production procedureof the multilayer ceramic capacitor shown in FIG. 1; and

FIG. 3A and FIG. 3B are schematic views showing a production procedureof a green sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, the present invention will be explained based on an embodimentshown in the drawings.

First, as an embodiment of an electronic device produced by using agreen sheet coating material (dielectric paste) and a green sheetaccording to the present invention, an overall configuration of amultilayer ceramic capacitor will be explained.

As shown in FIG. 1, a multilayer ceramic capacitor 2 according to thepresent embodiment comprises a capacitor element 4, a first terminalelectrode 6 and a second terminal electrode 8. The capacitor element 4comprises dielectric layers 10 and internal electrode layers 12, and theinternal electrode layers 12 are stacked alternately between thedielectric layers 10. The alternately stacked internal electrode layers12 on one side are electrically connected to inside of the firstterminal electrode 6 formed at one end portion of the capacitor element4. Also, the alternately stacked internal electrode layers 12 on theother side are electrically connected to inside of the second terminalelectrode 8 formed at the other end portion of the capacitor element 4.

A material of the dielectric layer 10 is not particularly limited andcomposed of a dielectric material, for example, calcium titanate,strontium titanate and/or barium titanate, etc. A thickness of each ofthe dielectric layers 10 is not particularly limited, but those having athickness of several μm to several hundreds of μm are general.Particularly in the present embodiment, it is made to be thin aspreferably 5 μm or less, and more preferably 3 μm or less.

A material of the terminal electrodes 6 and 8 is not particularlylimited, either, and copper, a copper alloy, nickel and a nickel alloy,etc. are normally used. Silver or an alloy of silver and palladium maybe also used. A thickness of the terminal electrodes 6 and 8 is notparticularly limited, either, but is normally 10 to 50 μm or so.

A shape and size of the multilayer ceramic capacitor 2 may be suitablydetermined in accordance with the object and use. When the multilayerceramic capacitor 2 has a rectangular parallelepiped shape, it isnormally a length (0.6 to 5.6 mm, preferably 0.6 to 3.2 mm)×width (0.3to 5.0 mm, preferably 0.3 to 1.6 mm)×thickness (0.1 to 1.9 mm,preferably 0.3 to 1.6 mm) or so.

Next, an example of production methods of the multilayer ceramiccapacitor 2 according to the present embodiment will be explained.

(1) First, a dielectric coating material (green sheet coating material)is prepared to produce a ceramic green sheet for composing thedielectric layers 10 shown in FIG. 1 after firing.

The dielectric coating material is composed of an organic solvent basedcoating material obtained by kneading a dielectric material (ceramicpowder) and an organic vehicle.

The dielectric material is suitably selected from a variety of compoundswhich become composite oxides or oxides, such as carbonates, nitrites,hydroxides, and organic metal compounds, and mixed for use. Thedielectric material is normally used as powder having an averageparticle diameter of 0.1 to 3 μm, and preferably 0.4 μm or less or so.Note that it is preferable to use finer powder than the green sheetthickness to form an extremely thin green sheet.

The organic vehicle is obtained by dissolving a binder resin in anorganic solvent. As the binder resin used for the organic vehicle, apolyvinyl butyral resin is used in the present embodiment. Apolymerization degree of the polybutyral resin is 1000 or higher and1700 or lower, and preferably 1400 to 1700. Also, a butyralation degreeof the resin is 64% or higher and 78% or lower, and preferably 64% orhigher and 70% or lower, and the residual acetyl group amount is lessthan 6% and preferably 3% or less.

The polymerization degree of the polybutyral resin can be measured, forexample, by a polymerization degree of a polyvinyl acetal resin as amaterial. Also, the butyralation degree can be measured, for example,based on the JISK6728. Furthermore, the residual acetyl group amount canbe measured based on the JISK6728.

When the polymerization degree of the polybutyral resin is too low, itis liable that sufficient mechanical strength is hard to be obtainedwhen made to be a thin film of, for example, 5 μm or less, andpreferably 3 μm or less or so. Also, when the polymerization degree istoo large, surface roughness tends to decline when made to be a sheet.Also, when the butyralation degree of the polybutyral resin is too low,solubility in a coating material tends to decline, while when too high,sheet surface roughness tends to decline. Furthermore, when the residualacetyl group amount is too large, sheet surface roughness tends todecline.

An organic solvent to be used for an organic vehicle includes a firstsolvent medium having a relatively low boiling point, wherein a binderresin is easy to be dissolved, and a second solvent medium having ahigher boiling point than that of the first solvent medium. In thepresent invention, the low boiling-point and the high boiling point arebased on a concept of relativity, and a solvent having a higher boilingpoint by 60 to 150° C. than that of alcohol having the lowest boilingpoint included in the first solvent medium can be defined as a solventhaving a high boiling point, and a solvent having a lower boiling pointthan that can be defined as a solvent having a low boiling point.

Alternately, a solvent having a higher boiling point by 50 to 105° C.than a drying temperature at the time when the green sheet coatingmaterial is made to be a sheet is defined as a solvent having a highboiling point, and a solvent having a lower boiling point than that canbe defined as a solvent having a low boiling point. Note that,temperature of drying the sheet is normally 50 to 100° C., morepreferably 60 to 80° C.

Alternately, those having a higher boiling point in a range of 130 to230° C., and more preferably in a range of 135 to 205° C. are defined asa solvent having a high boiling point, and those having a lower boilingpoint than that can be defined as a solvent having a lo boiling point.

A solvent having a high boiling point generally tends to have a lowvapor pressure. Therefore, in the present embodiment, a vapor pressureof the second solvent medium is lower than that of the first solventmedium at a predetermined temperature close to the room temperature. Forexample, the vapor pressure of the second solvent medium is 0.1 to 10%of that of alcohol having the highest vapor pressure included in thefirst solvent medium. Specifically, a vapor pressure of the secondsolvent medium at 25° C. is in a range of 1.3 to 667 Pa (0.01 to 5Torr), and more preferably in a range of 10 to 300 Pa.

When assuming that a boiling point of the second solvent medium is T° C.and a vapor pressure of the second solvent medium at 25° C. is α Pa, aproduct of T×α is in a range of 2000 to 65000 (° C.×Pa), and morepreferably in a range of 3000 to 50000. Since a rising rate of a boilingpoint is larger than a lowering rate of a vapor pressure, the product ofT×α in the ranges is preferable. Note that there are some solvents,wherein the vapor pressure is high even if the boiling point is high. Inthe present invention, it is preferable that the solvent having a highboiling point and a low vapor pressure is included as the second solventmedium.

The first solvent medium is not particularly limited as far as it has alow boiling point and a butyral based resin is dissolved therein.Preferably, at least one of ethanol and methanol is included.

The second solvent medium is not particularly limited as far as it has ahigh boiling point and a butyral based resin can be dissolved therein,but at least one selected from 1) to 3) below is included.

1) monohydric alcohol having a carbon number of 5 to 9

1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, tarpineol

2) ketones containing a cyclic structure

cyclohexanon, isophorone

3) compound containing two or more functional groups selected from a —OHgroup, ether and ketone

2-ethoxyethanol, 2-butoxyethanol, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diacetone alcohol

Among them, as the second solvent medium, diethylene glycol monoethylether, 2-butoxyethanol, diacetone alcohol and 1-pentanol areparticularly preferable.

The second solvent medium is included preferably by 5 to 70 wt %, andmore preferably 30 to 70 wt % with respect to 100 wt % of the entiresolvent. When the content of the second solvent medium is too small,effects of the present invention are small, while when too much, ittends to be difficult to make a sheet.

Furthermore, in the present embodiment, as a solvent, an alcohol basedsolvent and aromatic solvent are preferably included, and an aromaticsolvent is included by 6 parts by weight or more and 20 parts by weightor less when assuming that the total weight of the alcohol based solventand the aromatic solvent is 100 parts by weight. When the content of thearomatic solvent is too small, surface roughness of the sheet tends toincrease, while when too much, the coating material filtrationproperties decline and sheet surface roughness also declines byincreasing.

As an alcohol based solvent, methanol, ethanol, propanol and butanol,etc. may be mentioned. As an aromatic solvent, toluene, xylene andbenzyl acetate, etc. may be mentioned.

A binder resin is dissolved in an alcohol based solvent and filtrated toobtain a solution in advance, and dielectric powder and other componentsare added to the solution. A binder resin having a high polymerizationdegree is hard to be dissolved in a solvent, and dispersibility of acoating material tends to decline in a normal method. In a method of thepresent embodiment, a binder resin having a high polymerization degreeis dissolved in the above good solvent and ceramic powder and othercomponents are added to the solution, so that dispersibility of acoating material can be improved and generation of undissolved resin canbe suppressed. Note that solid content concentration cannot be raisedand changes of lacquer viscosity tend to become large over time in thecase of a solvent other than the above solvents.

In the present embodiment, in the dielectric coating material, a xylenebased resin is preferably added as a tackifier together with a binderresin. The xylene based resin is added in a range of 1.0 wt % or less,more preferably 0.1 wt % or more and 1.0 wt % or less, and particularlypreferably in a range of more than 0.1 and 1.0 wt % or less with respectto 100 parts by weight of ceramic powder. When the adding quantity ofthe xylene based resin is too small, adhesiveness tends to decline.While when the adding quantity is too much, adhesiveness improves but itis liable that surface roughness of the sheet declines, stacking by alarge number becomes difficult, tensile strength of the sheet declines,and handlability of the sheet decline.

In the dielectric coating material, additives selected from a variety ofdispersants, plasticizers, antistatic agents, dielectrics, glass flit,and insulators may be included in accordance with need.

In the present embodiment, a dispersant is not particularly limited, butpolyethylene glycol based nonionic dispersant is preferably used, and ahydrophile-lipophile balance (HLB) value thereof is 5 to 6. A dispersantis added by 0.5 part by weight or more and 1.5 parts by weight or less,and more preferably 0.5 part by weight or more and 1.0 part by weight orless with respect to 100 parts by weight of ceramic powder.

When the HLB is out of the above ranges, it is liable that coatingmaterial viscosity increases and sheet surface roughness increases.Also, in the case of a dispersant other than a polyethylene glycol basednonionic dispersant, coating material viscosity increases, sheet surfaceroughness increases and sheet ductility declines, so that it is notpreferable.

When an adding quantity of a dispersant is too small, sheet surfaceroughness tends to increase, while when too large, sheet tensilestrength and stackability tend to decline.

In the present embodiment, dioctyl phthalate is preferably used as aplasticizer and contained by an amount of preferably 40 parts by weightor more and 70 parts by weight or less, and more preferably 40 to 60parts by weight with respect to 100 parts by weight of a binder resin.Comparing with other plasticizers, dioctyl phthalate is preferable interms of both of sheet strength and sheet stretch and is particularlypreferable for having weak peeling strength so as to be easily peeledfrom a supporting body. Note that when a content of the plasticizer istoo small, it is liable that sheet stretch becomes less and flexibilitybecomes less. Also, when the content is too large, it is liable thatbreedout of a plasticizer from a sheet is caused, segregation of theplasticizer against the sheet easily arises and dispersibility of thesheet declines.

Also, in the present embodiment, the dielectric coating materialcontains water by 1 part by weight or more and 6 parts by weight orless, and preferably 1 to 3 parts by weight with respect to 100 parts byweight of dielectric powder. When a water content is too small, changesof coating material characteristics due to moisture absorbance over timebecomes large, which is preferable, coating material viscosity tends toincrease and filtration properties of the coating material tend todecline. While when the water content is too large, separation andprecipitation of the coating material are caused, the dispersibilitybecomes poor and surface roughness of the sheet tends to decline.

Furthermore, in the present embodiment, at least any one of ahydrocarbon based solvent, industrial gasoline, kerosene, and solventnaphtha is added by preferably 3 parts by weight or more and 15 parts byweight, and more preferably 5 to 10 parts by weight with respect to 100parts by weight of dielectric powder. By adding these additives, sheetstrength and sheet surface roughness can be improved. When an addingquantity of these additives is too small, effects of adding is small,while when the adding quantity is too large, it is liable that sheetstrength and sheet surface roughness are deteriorated inversely.

A binder resin is contained preferably by 5-parts by weight or more and6.5 parts by weight or less with respect to 100 parts by weight ofdielectric powder. When a content of the binder resin is too small, itis liable that the sheet strength declines and stackability(adhesiveness at the time of stacking in layers) also declines. Whilewhen a content of the binder resin is too large, it is liable thatsegregation of the binder resin is caused to make the dispersibilityworse and sheet surface roughness tends to decline.

When assuming that total volume of the ceramic powder, binder resin andplasticizer is 100 volume %, a volume ratio accounted by the dielectricpowder is preferably 62.42% or more and 72.69% or less, and morepreferably 63.93% or more and 72.69% or less. When the volume ratio istoo small, it is liable that segregation of the binder is easily causedto make the dispersibility worse and surface roughness declines. Also,when the volume ratio is too large, it is liable that the sheet strengthdeclines and the stackability also declines.

Furthermore, in the present embodiment, the dielectric coating materialpreferably includes an antistatic agent, and the antistatic agent ispreferably imidazoline based antistatic agent. When the antistatic agentis not an imidazoline based antistatic agent, the antistatic effect issmall and the sheet-strength, sheet ductility or adhesiveness tends todecline.

An antistatic agent is contained by 0.1 part by weight or more and 0.75part by weight or less, and more preferably 0.25 to 0.5 part by weightwith respect to 100 parts by weight of ceramic powder. When an addingquantity of the antistatic agent is too small, the antistatic effectbecomes small, while when too large, it is liable that surface roughnessof the sheet declines and sheet strength declines. When the antistaticeffect is too small, electrostatic easily arises when peeling thecarrier sheet as a supporting body from the ceramic green sheet, and adisadvantage that the green sheet gets wrinkled, etc. easily arises.

By using the dielectric coating material, as shown in FIG. 2, a greensheet 10 a is formed to be a thickness of preferably 0.5 to 30 μm, andmore preferably 0.5 to 10 μm or so on the carrier sheet 30 as a secondsupporting sheet by the doctor blade method, etc. The green sheet 10 ais dried after being formed on the carrier sheet 30.

Temperature of drying the green sheet is preferably 50 to 100° C. anddrying time is preferably 1 to 20 minutes. A thickness of the greensheet after drying is contracted to 5 to 25% of that before drying. Thethickness of the green sheet 10 a after drying is preferably 3 μm orless.

When drying the green sheet 10 a, in the present embodiment, as shown inFIG. 3B, as a solvent, other than the first solvent medium having arelatively low boiling point, wherein a binder resin is easy to bedissolved, a second solvent medium having a higher boiling point thanthat of the first solvent medium is included in the coating material.Accordingly, an evaporation rate of the solvent from the green sheetbecomes low and the sheet surface becomes smooth even in the case of anextremely thin green sheet.

Note that, as shown in FIG. 3A, in the case of a coating materialincluding only the first solvent medium as a solvent, the evaporationrate becomes high and the sheet surface tends to become rough.

(2) As shown in FIG. 2, a carrier sheet 20 as a first supporting sheetis prepared separately from the above carrier sheet 30, and a releaselayer 22 is formed thereon, and on top thereof, an electrode layer 12 ahaving a predetermined pattern is formed. On a surface of the releaselayer 22 where the electrode layer 12 a is not formed, a blank patternlayer 24 having substantially the same thickness as that of theelectrode layer 12 a is formed.

As the carrier sheets 20 and 30, for example, a PET film, etc. is used,and those coated with silicon, etc. are preferable to improve therelease property. Thicknesses of the carrier sheets 20 and 30 are notparticularly limited and are preferably 5 to 100 μm.

The release layer 22 preferably contains the same dielectric powder asthe dielectric composing the green sheet 10 a. Also, the release layer22 contains a binder, a plasticizer and a release agent other than thedielectric powder. A particle diameter of the dielectric powder may bethe same as that of the dielectric particles included in the green sheetbut it is preferable to be smaller.

In the present embodiment, a thickness of the release layer 22 ispreferably not more than a thickness of the electrode layer 12 a, andmore preferably, it is set to be a thickness of 60% or less, and furtherpreferably 30% or less.

A method of applying the release layer 22 is not particularly limited,but it has to be formed to be extremely thin, so that an applying methodusing, for example, a wire bar coater or a die coater is preferable.Note that adjustment of the release layer 22 thickness can be made byselecting a wire bar coater having a different wire diameter. Namely, tomake the thickness of the release layer to be applied thinner, it can bedone by selecting one having a small wire diameter, inversely, to formit thick, one with a large wire diameter may be selected. The releaselayer 22 is dried after being applied. The drying temperature ispreferably 50 to 100° C. and the drying time is preferably 1 to 10minutes.

A binder for the release layer 22 is composed, for example, of anacrylic resin, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol,polyolefin, polyurethane, polystyrene, or an organic composed of acopolymer of these or emulsion. The binder contained in the releaselayer 22 may be the same as the binder contained in the green sheet 10 aor may be different from that, but preferably the same.

A plasticizer for the release layer 22 is not particularly limited and,for example, phthalate ester, dioctyl phthalate, adipic acid, phosphateester and glycols, etc. may be mentioned. The plasticizer to becontained in the release layer 22 may be the same as that contained inthe green sheet or may be different from that.

A release agent for the release layer 22 is not particularly limitedand, for example, paraffin, wax and silicone oil, etc. may be mentioned.A release agent contained in the release layer 22 may be the same asthat contained in the green sheet or may be different from that.

A binder is contained in the release layer 22 by preferably 2.5 to 200parts by weight, more preferably 5 to 30 parts by weight, andparticularly preferably 8 to 30 parts by weight or so with respect to100 parts by weight of dielectric particle.

A plasticizer is preferably contained in the release layer 22 by 0 to200 parts by weight, preferably 20 to 200 parts by weight, and morepreferably 50 to 100 parts by weight with respect to 100 parts by weightof the binder.

A release agent is preferably contained in the release layer 22 by 0 to100 parts by weight, preferably 2 to 50 parts by weight, and morepreferably 5 to 20 parts by weight with respect to 100 parts by weightof the binder.

After forming the release layer 22 on the surface of the carrier sheet,an electrode layer 12 a to compose an internal electrode layer 12 afterfiring is formed to be a predetermined pattern on the surface of therelease layer 22. A thickness of the electrode layer 12 a is preferably0.1 to 2 μm, and more preferably 0.1 to 1.0 μm or so. The electrodelayer 12 a may be configured by a single layer or two or more layershaving different compositions.

The electrode layer 12 a can be formed on the surface of the releaselayer 22 by a thick film formation method, such as a printing methodusing an electrode coating material, or a thin film method, such asevaporation and sputtering. When forming the electrode layer 12 a on thesurface of the release layer 22 by a screen printing method or a gravureprinting method as a kind of thick film method, it is as follows.

First, an electrode coating material is prepared. The electrode coatingmaterial is fabricated by kneading a conductive material composed of avariety of conductive metals and alloys, or a variety of oxides, organicmetal compounds or resinates, etc. to be conductive materials afterfiring with an organic vehicle.

As a conductive material to be used when producing the electrode coatingmaterial, Ni, a Ni alloy and a mixture of these are used. A shape of theconductive materials is not particularly limited and may be a sphericalshape and scale-like shape, etc. or a mixture of these shapes. Thosehaving an average particle diameter of the conductive material ofnormally 0.1 to 2 μm, and preferably 0.2 to 1 μm or so may be used.

An organic vehicle contains a binder and a solvent. As the binder, forexample, ethyl cellulose, an acrylic resin, polyvinyl butyral, polyvinylacetal, polyvinyl alcohol, polyolefin, polyurethane, polystyrene, or acopolymer of these may be mentioned. Particularly, butyrals, such aspolyvinyl butyral, are preferable.

The binder is contained in the electrode coating material by preferably8 to 20 parts by weight with respect to 100 parts by weight of theconductive material (metal powder). As a solvent, any of well-knownones, such as terpionel, butylcarbitol and kerosene, may be used. Acontent of the solvent is preferably 20 to 55 wt % or so with respect tothe entire coating material.

To improve the adhesiveness, the electrode coating material preferablycontains a plasticizer. As a plasticizer, benzylbutyl phthalate (BBP)and other phthalate esters, adipic acids, phosphoric esters, andglycols, etc. may be mentioned. The plasticizer in the electrode coatingmaterial is preferably 10 to 300 parts by weight, and more preferably 10to 200 parts by weight with respect to 100 parts by weight of thebinder. Note that when an adding quantity of the plasticizer or adhesiveis too large, it is liable that strength of the electrode layer 12 aremarkably declines. Also, to improve transferability of the electrodelayer 12 a, it is preferable to improve adhesiveness and/or adherence ofthe electrode coating material by adding a plasticizer and/or adhesivein the electrode coating material.

After or before forming the electrode coating material layer in apredetermined pattern on the surface of the release layer 22 by aprinting method, a blank pattern layer 24 is formed to be substantiallythe same thickness as that of the electrode layer 12 a on the surface ofthe release layer 22 not formed with the electrode layer 12 a. The blankpattern layer 24 is composed of the same material as that of the greensheet and formed by the same method. The electrode layer 12 a and theblank layer 24 are dried in accordance with need. The drying temperatureis not particularly limited, but is preferably 70 to 120° C., and thedrying time is preferably 5 to 15 minutes.

(3) After that, the electrode layer 12 a is adhered to the surface ofthe green sheet 10 a. For that purpose, the electrode layer 12 a and theblank pattern layer 24 are pressed against the surface of the greensheet 10 a together with the carrier sheet 20, heated and pressed totransfer the electrode layer 12 a and the blank pattern layer 24 to thesurface of the green sheet 10 a. Note that when seeing from the greensheet side, the green sheet 10 a is transferred to the electrode layer12 a and the blank pattern layer 24.

Heating and pressing at the time of transferring may be pressing andheating by a press or by a calendar roll, but is preferably performed bya pair of rolls. The heating temperature and the pressing force are notparticularly limited.

By stacking single-layered green sheets formed with an electrode layer12 a of a predetermined pattern on a green sheet 10 a, a stacked block,wherein a large number of the electrode layers 12 a and the green sheet10 a are alternately stacked, is obtained. After that, an outer layergreen sheet (a little thicker stacked body, wherein a plurality of greensheets not formed with an electrode layer are stacked) is stacked on thelower surface of the stacked body. After that, an outer layer greensheet is formed in the same way on the upper side of the stacked body,then, a final pressing is performed.

Pressure at the time of the final pressing is preferably 10 to 200 MPa.Also, the heating temperature is preferably 40 to 100° C. After that,the multilayer body is cut to be a predetermined size to form greenchips. The green chips are subjected to binder removal processing andfiring processing, then, thermal treatment is performed in order tore-oxidize the dielectric layer.

The binder removal processing may be performed under a normal condition,but when using a base metal, such as Ni and a Ni alloy, as a conductivematerial of the internal electrode layer, it is preferably performedunder the specific condition below.

temperature rising rate: 5 to 300° C./hour, particularly 10 to 50°C./hour

holding temperature: 200 to 400° C., particularly 250 to 350° C.

holding time: 0.5 to 20 hours, particularly 1 to 10 hours

atmosphere: a mixed gas of wet N₂ and H₂

A firing condition is preferably as below.

temperature rising rate: 50 to 500° C./hour, particularly 200 to 300°C./hour

holding temperature: 1100 to 1300° C., particularly 1150 to 1250° C.

holding time: 0.5 to 8 hours, particularly 1 to 3 hours

cooling rate: 50 to 500° C./hour, particularly 200 to 300° C./hour

atmosphere gas: a mixed gas of wet N₂ and H₂, etc.

Note that oxygen partial pressure in an atmosphere in the air at firingis preferably 10⁻² Pa or less, particularly 10⁻² to 10⁻⁸ Pa. Whenexceeding the above ranges, the internal electrode layer tends tooxidize, while when the oxygen partial pressure is too low, abnormalsintering is caused in an electrode material of the internal electrodelayer to be broken.

The thermal treatment after performing such firing is preferablyperformed with a holding temperature or highest temperature of 1000° C.or higher, more preferably 1000 to 1100° C. When the holding temperatureor the highest temperature at the time of the thermal treatment is lowerthan the above ranges, it is liable that oxidization of the dielectricmaterial is insufficient to make the insulation resistance lifetimeshort, while when exceeding the above ranges, Ni in the internalelectrode oxidizes and the capacity decreases, moreover, Ni reacts witha dielectric base and the lifetime also tends to become short. Theoxygen partial pressure at the time of thermal treatment is higher thana higher oxygen partial pressure than a reducing atmosphere at the timeof firing, preferably 10⁻³ Pa to 1 Pa, and more preferably 10⁻² Pa to 1Pa. When it is lower than the above range, re-oxidization of thedielectric layer 2 becomes difficult, while when exceeding the aboveranges, the internal electrode layer 3 tends to oxidize. Other conditionof the thermal treatment is preferably as below.

holding time: 0 to 6 hours, particularly 2 to 5 hours

cooling rate: 50 to 500° C./hour, particularly 100 to 300° C./hour

atmosphere gas: wet N₂ gas, etc.

Note that to wet a N₂ gas or a mixed gas, etc., for example, a wetter,etc. may be used. In this case, the water temperature is preferably 0 to75° C. or so. Also, the binder removal processing, firing and thermaltreatment may be performed continuously or separately. When performingcontinuously, the atmosphere is changed without cooling after the binderremoval processing, continuously, the temperature is raised to theholding temperature at firing to perform firing. Next, it is cooled andthe thermal treatment is preferably performed by changing the atmospherewhen the temperature reaches to the holding temperature of the thermaltreatment. On the other hand, when performing them separately, afterraising the temperature to the holding temperature at the binder removalprocessing in an atmosphere of a N₂ gas or a wet N₂ gas, the atmosphereis changed, and the temperature is furthermore raised. After cooling thetemperature to the holding temperature at the thermal treatment, it ispreferable that the cooling continues by changing the atmosphere againto a N₂ gas or a wet N₂ gas. Also, in the thermal treatment, afterraising the temperature to the holding temperature under the N₂ gasatmosphere, the atmosphere may be changed, or the entire process of thethermal processing may be in a wet N₂ gas atmosphere.

The thus obtained sintered body (element body 4) is subjected to endsurface polishing, for example, by barrel polishing and sand-blast,etc., then, a terminal electrode coating material is burnt to formterminal electrodes 6 and 8. For example, a firing condition of theterminal electrode coating material is preferably in a mixed gas of wetN₂ and H₂ at 600 to 800° C. for 10 minutes to 1 hour or so. Inaccordance with need, soldering, etc. is performed on the terminalelectrodes 6 and 8 to form a pad layer. Note that the terminal electrodecoating material may be fabricated in the same way as the electrodecoating material explained above.

A multilayer ceramic capacitor of the present invention produced asabove is mounted on a print substrate, etc. by soldering, etc. and usedfor a variety of electronic equipments.

In a method of producing a multilayer ceramic capacitor using thedielectric coating material (green sheet coating material) and the greensheet according to the present embodiment, by using a binder resinincluding a butyral based resin as the main component and by containingthe second solvent medium having a higher boiling point than that of thefirst solvent medium other than the first solvent medium having arelatively low boiling point, wherein the binder resin is easy to bedissolved, it becomes possible to produce a green sheet without a pinhole having enough strength to be peeled from a supporting body andexcellent surface smoothness even if the green sheet was extremely thin.For example, a thickness of a dielectric layer after firing (a greensheet after firing) can be made as thin as 5 μm or less, preferably 3 μmor less, and furthermore preferably 2 μm or less. Also, the number oflayers to be stacked can be increased. Furthermore, short-circuiting orother defects can be reduced.

Also, in a production method of a multilayer ceramic capacitor using thedielectric coating material (green sheet coating material) and the greensheet according to the present embodiment, a specific kind of dispersanthaving a specific range of HLB is used. Therefore, even an extremelythin green sheet of, for example, 5 μm or thinner is strong enough to bepeeled from the carrier sheet and has preferable adhesiveness andhandlability. Also, surface roughness of the sheet is small andstackability is excellent. Therefore, it becomes easy to stack a largenumber of green sheets via electrode layers.

Furthermore, in a production method of a multilayer ceramic capacitorusing the dielectric coating material (green sheet coating material) andthe green sheet according to the present embodiment, an antistatic agentis contained in the dielectric coating material, and the antistaticagent is an imidazoline based antistatic agent. Therefore, even in thecase of an extremely thin green sheet of, for example, 5 μm or thinner,it is possible to produce a green sheet having sufficient strength to bepeeled from the carrier sheet, wherein static electricity generated atthe time of being peeled from the carrier sheet is suppressed, and theadhesiveness and handlability are preferable. Also, surface roughness ofthe sheet is small and stackability is excellent. Therefore, it becomeseasy to stack a large number of green sheets via electrode layers.

Also, in a production method of a multilayer ceramic capacitor accordingto the present embodiment, a dry type electrode layer can be easily andhighly accurately transferred to the surface of the green sheet withoutdamaging or deforming the green sheet.

Note that the present invention is not limited to the above embodimentsand may be variously modified within the scope of the present invention.

For example, a method of the present invention is not limited to theproduction method of multilayer ceramic capacitors and may be applied asa production method of other multilayer type electronic devices.

Below, the present invention will be explained based on further detailedexamples, but the present invention is not limited to the examples.

EXAMPLE 1a Production of Green Sheet Coating Material

As a starting material of ceramic powder, BaTiO₃ powder (BT-02 made bySakai Chemical Industry Co., Ltd.) was used. A ceramic powdersubcomponent-additives were prepared to satisfy (Ba_(0.6)Ca_(0.4))SiO₃:1.48 parts by weight, Y₂O₃: 1.01 parts by weight, MgCO₃: 0.72 wt %,Cr₂O₃: 0.13 wt % and V₂O₅: 0.045 wt % with respect to 100 parts byweight of the BaTiO₃ powder.

First, only the subcomponent additives were mixed by a ball-mill toobtain slurry. Namely, the subcomponent additives (total amount 8.8 g),15 g of a solvent, wherein a ratio of ethanol, n-propanol and xylene is42.5:42.5:15, a dispersant (0.1 g) and a binder (2 wt % (1.1 g as alacquer adding quantity) of the subcomponent additives) were preliminaryground by a ball-mill for 20 hours, and preliminary ground slurry wasobtained.

Next, with respect to 191.2 g of BaTiO₃, the preliminary ground slurryof the subcomponent additives: 24 g, ethanol: 123 g, n-propanol: 123 g,xylene: 56 g, diethylene glycol monoethyl ether (DGME): 136 g, mineralspirit: 15 g, a dispersant: 1.4 g, DOP (dioctyl phthalate): 6 g, animidazoline based antistatic agent: 0.8 g, lacquer of BH-6 (a polyvinylbutyral resin BH-6 made by Sekisui Chemical Co., Ltd. was dissolved inethanol/n-propanol=1:1): 80 g were mixed by a ball mill for 20 hours toobtain a ceramic coating material (green sheet coating material).

Note that, as a dispersant, a polyethylene glycol based nonionicdispersant (HLB=5 to 6) was used. As a binder, 15% lacquer (BH6 made bySekisui Chemical Co., Ltd. was dissolved in ethanol/n-propanol=1:1) ofBH6 made by Sekisui Chemical Co., Ltd. (polybutyral resin (PVB)) wasadded as a solid content.

Solvent components in the ceramic coating material include a solventhaving a low boiling point composed of ethanol and n-propanol (a firstsolvent medium) and a solvent having a high boiling point composed ofDGME (a second solvent medium). A content of the solvent having a highboiling point (the second solvent medium) in the solvent was 26 wt %with respect to the entire solvent of 100 wt %. Note that a boilingpoint and a vapor pressure at 25° C. are shown in Table 1.

A polymerization degree of the polybutyral resin as a binder resin was1400, a butyralation degree thereof was 69±3%, and a residual acetylgroup amount thereof was 3±2%. The binder resin was contained by 6 partsby weight in the ceramic coating material with respect to 100 parts byweight of ceramic powder (including ceramic powder subcomponentadditives). Also, when assuming that total volume of the ceramic powder,binder resin and plasticizer in the ceramic coating material was 100volume %, the volume ratio accounted by the ceramics powder was 67.31volume %.

Also, DOP as a plasticizer was contained in the ceramic coating materialby 50 parts by weight with respect to 100 parts by weight of the binderresin. Water was contained by 2 parts by weight with respect to 100parts by weight of the ceramic powder. The polyethylene glycol basednonionic dispersant as a dispersant was contained by 0.7 part by weightwith respect to 100 parts by weight of the ceramic powder.

Also, in the coating material, mineral spirit of at least any one of ahydrocarbon based solvent, industrial gasoline, kerosene and solventnaphtha was added by 5 parts by weight with respect to 100 parts byweight of the ceramic powder.

Viscosity of the coating material was 180 mPa·S. The viscosity of thecoating material was measured by using a B-type viscosimeter and usingS21 as a rotor, and measurement was made at a temperature of 25°immediately after the coating material was obtained. The rotation rateat the time of measurement was 50 rpm.

Production of Green Sheet

The coating material obtained as above was applied to a PET film as asupporting film by a wire bar coater and dried, so that a green sheethaving a thickness of 1 μm was produced. The applying rate was 50 m/min.and the drying condition was a temperature in the drying furnace of 60°C. to 70° C. and drying time of 2 minutes.

Evaluation of Green Sheet

After that, a degree of brilliancy of the green sheet was measured. Thedegree of brilliancy was obtained by measuring a degree of brilliancy onthe green sheet surface by using VGS-1D made by Nippon Denshoku Co.,Ltd. based on the JIS Z-8741 (1983) method. The higher a percentage ofthe degree of brilliance is, the more excellent in surface smoothness.The results are shown in Table 1. In the measurement of the degree ofbrilliance, those with 38% or higher were determined to be good (o) andthe rest were determined to be defect (x). TABLE 1 Sheet of 1 μm VaporPressure at 25° C. Evaluation Name of Boiling Boiling Point × Degree onDegree Solvent Having Point Vapor Pressure Vapor Pressure of Brillianceof Brilliance High Boiling Point [° C.] [Pa] [° C. · Pa] [%] [∘ or x]Comparative Example 1a 1-decanol 231 0.8 185 — x Not Dried Example laDGME 202 17.3 3501 66.1 ∘ Example 1b 2BE 170 113.6 19333 59.2 ∘ Example1c DAA 168 226.6 38100 55.5 ∘ Example 1d 1P 138 290.0 40017 50.3 ∘Comparative Example 1b 1-butanol 118 861.8 101433 32.1 x ComparativeExample 1c xylene 140 1100.4 154062 36.0 x

EXAMPLE 1b

Other than using 2-butoxy ethanol (2BE) instead of DGME as a solventhaving a high boiling point, a green sheet was produced in the same wayas in the example 1a, and the same evaluation was made. The results areshown in Table 1.

EXAMPLE 1c

Other than using diacetone alcohol (DAA) instead of DGME as a solventhaving a high boiling point, a green sheet was produced in the same wayas in the example 1a, and the same evaluation was made. The results areshown in Table 1.

EXAMPLE 1d

Other than using 1-pentanol (1P) instead of DGME as a solvent having ahigh boiling point, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 1.

COMPARATIVE EXAMPLE 1a

Other than using 1-decanol instead of DGME as a solvent having a highboiling point, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 1.

COMPARATIVE EXAMPLE 1b

Other than using 1-butanol instead of DGME as a solvent having a highboiling point, a green sheet was produced in the same way as in theexample 1a, and the same evaluation was made. The results are shown inTable 1.

COMPARATIVE EXAMPLE 2a

Except that a solvent having a high boiling point is not included, agreen sheet was produced in the same way as in the example 1a, and thesame evaluation was made. The results are shown in Table 2. TABLE 2Sheet of 1 μm Name of Adding Evaluation Solvent Having Quantity Degreeof on Degree High Boiling Ratio Brilliance of Brilliance Point [wt %][%] [∘ or x] Comparative non-addition 0.0 36.0 x Example 2a Example 2aDAA 8.8 38.0 ∘ Example 2b DAA 13.0 38.2 ∘ Example 2c DAA 26.1 46.6 ∘Example 2d DAA 39.1 52.0 ∘ Example 2e DAA 52.1 55.5 ∘ Example 2f DAA63.0 42.5 ∘ Comparative DAA 75.0 — x Example 2b

EXAMPLES 2a TO 2f AND COMPARATIVE EXAMPLE 2b

Other than using DAA instead of DGME as a solvent having a high boilingpoint and changing the adding quantity (including xylene) to 8.8 to 75wt % with respect to 100 wt % of the entire solvent, a green sheet wasproduced in the same way as in the example 1a, and the same evaluationwas made. The results are shown in Table 2. Note that since an addingquantity was too much in the comparative example 2b, it was not possibleto make a sheet without drying.

Evaluation

As shown in Table 1, as a result that a solvent having a high boilingpoint, wherein the boiling point was in a range of 130 to 230° C., wasincluded in the ceramic coating material, it was confirmed that a degreeof brilliance of the sheet improved and surface smoothness of the sheetimproved.

Also, as shown in Table 1, when assuming that a boiling point of asolvent is T° C. and a vapor pressure of the second solvent medium at25° C. is α Pa, it was confirmed that a degree of brilliance of thesheet improved and surface smoothness of the sheet improved when aproduct of T×α is in a range of 2000 to 65000 (° C. ×Pa), and morepreferably in a range of 3000 to 50000 (° C.×Pa).

Furthermore, as shown in Table 2, as a result that a solvent having ahigh boiling point was included by 5 to 70 wt %, and more preferably 8to 52 wt % with respect to 100 wt % of the entire solvent, it wasconfirmed that a degree of brilliance of the sheet improved and surfacesmoothness of the sheet improved.

As explained above, according to the present invention, it is possibleto provide a coating material, a green sheet and a method capable ofproducing a green sheet without a pin hole, having enough strength to bepeeled from a supporting body and excellent surface smoothness even whenthe green sheet is extremely-thin, and being suitable to make anelectronic device thinner and multilayered.

1. A green sheet coating material containing ceramic powder, a binderresin including a butyral based resin as the main component, and asolvent, wherein said solvent contains a first solvent medium having arelatively low boiling point, wherein said binder resin is easy to bedissolved, and a second solvent medium having a relatively high boilingpoint.
 2. The green sheet coating material as set forth in claim 1,wherein said second solvent medium contains at least one selectedfrom 1) monohydric alcohol having a carbon number of 5 to 9, 2) ketonescontaining a cyclic structure and 3) compounds containing two or morefunctional groups selected from a —OH group, ether and ketone.
 3. Thegreen sheet coating material as set forth in claim 1, wherein a vaporpressure of said second solvent medium at the room temperature is lowerthan that of said first solvent medium.
 4. The green sheet coatingmaterial as set forth in claim 1, wherein a boiling point of said secondsolvent medium is in a range of 130 to 230° C.
 5. The green sheetcoating material as set forth in claim 1, wherein a vapor pressure ofsaid second solvent medium at 25° C. is in a range of 1.3 to 667 Pa. 6.The green sheet coating material as set forth in claim 1, wherein, whenassuming that a boiling point of said second solvent medium is T° C. anda vapor pressure of said second solvent medium at 25° C. is α Pa, aproduct of T×α is in a range of 2000 to 65000 (° C.×Pa).
 7. The greensheet coating material as set forth in claim 1, wherein said secondsolvent medium has a higher boiling point by 50 to 105° C. than a dryingtemperature at the time of making said green sheet coating material tobe a sheet.
 8. The green sheet coating material as set forth in claim 1,wherein said second solvent medium is included by 5 to 70 wt % withrespect to 100 wt % of the entire solvent.
 9. The green sheet coatingmaterial as set forth in claim 1, wherein said second solvent mediumincludes an organic solvent having a higher boiling point by 60 to 150°C. than that of alcohol having the lowest boiling point included in saidfirst solvent medium.
 10. The green sheet coating material as set forthin claim 1, wherein said second solvent medium includes an organicsolvent having a vapor pressure at 25° C. of 0.1 to 10% of that ofalcohol having the highest vapor pressure at 25° C. included in saidfirst solvent medium.
 11. The green sheet coating material as set forthin claim 1, wherein said second solvent medium includes at least oneselected from the 1) to 3) below. 1) monohydric alcohol having a carbonnumber of 5 to 9 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol,1-nonanol, tarpineol 2) ketones containing a cyclic structurecyclohexanon, isophorone 3) compound containing two or more functionalgroups selected from a —OH group, ether and ketone 2-ethoxyethanol,2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, diacetone alcohol
 12. The green sheet coating materialas set forth in claim 1, wherein said butyral based resin is apolybutyral resin; and a polymerization degree of said polybutyral resinis 1000 or more and 1700 or less, a butyralation degree of the resin is64% or higher and 78% or lower, and a residual acetyl group amount isless than 6%.
 13. The green sheet coating material as set forth in claim1, wherein said binder resin is included by 5 parts by weight or moreand 6.5 parts by weight or less with respect to 100 parts by weight ofsaid ceramic powder.
 14. A production method of a ceramic green sheet,comprising the steps of: preparing a green sheet coating material as setforth in claim 1; and forming a ceramic green sheet by using said greensheet coating material.
 15. The production method of a ceramic greensheet as set forth in claim 14, wherein a drying temperature at the timeof forming a ceramic green sheet by using said green sheet coatingmaterial is 50 to 100° C.
 16. A production method of a ceramicelectronic device, comprising the steps of: preparing a green sheetcoating material as set forth in claim 1; forming a ceramic green sheetby using said green sheet coating material; drying said green sheet;stacking the green sheets after drying via an internal electrode layerto obtain a green chip; and firing said green chip.
 17. The productionmethod of a ceramic electronic device as set forth in claim 16, whereina drying temperature at the time of drying said green sheet is 50 to100° C.
 18. A green sheet produced by using a green sheet coatingmaterial as set forth in claim 1.